References
- Gravel , D. , Bordeleau , L. , Ladouceur , G. , Rancourt , J. and Thoraval , D. 1984 . Can. J. Chem. , 62 : 2945 For salient references to the structure of selagine, and recent work toward its total synthesis, see
- All new compounds gave correct combustion or mass spectrometric analyses and IR as well as 300 MHz 1H-NMR spectra. Dione 3b: 1H-NMR (300 MHz, CDCl3): δ 5.80(1H,s), 3.80(3H,s), 3.32(1H,d,J=15), 2.95–2.83(3H,m), 2.75(1H,dd,J-15,3), 2.58(1H,dd,J=15,3), 2.44(1H,d,J-18), 1.76(3H,s). Decoupling experiments show that the proton at δ 2.44(C-2, axial) and the proton at δ 2.58(C-6, pseudoequatorial) each have large, (geminal) coupling to respective protons in the 2.83–2.95 multiplet, whereas that at δ 3.32(C-4,equatorial) is coupled only to its geminal C-4 axial partner at δ 2.75. These data confirm three distinct CH2 groups in 3b and preclude the possibility that this starting diketone has the rearranged [4.2.1]nonenedione skeleton generated during the subsequent carbanion reaction
- Kende , A. S. , Battista , R. A. and Sandoval , S. B. 1984 . Tetrahedron Lett. , 25 : 1341 The dimethyl ketal 3a was prepared according to the procedure previously reported, replacing ethylene glycol with methyl orthoformate. Its 300 MHz NMR spectrum was appropriately parallel to that of the dioxolane analog described in
- The new C-4 vinyl proton of the enamine unit showed a clean doublet at δ 4.15, J=5.8 Hz, indicating vicinal coupling to the C-5 bridgehead proton
- Woodward , R. B. , Pachter , I. J. and Scheinbaum , M. L. 1971 . J. Org. Chem. , 36 : 1137 See also Kuehne, M.E., J. Org. Chem. 1963, 28, 2124
- Dithiane 1: 1H-NMR (300 MHz, CDCl3): 5.48(1H,s), 4.16(1H,d,J=15), 3.78(3H,s), 3.54(1H,dt,J=13,2.5), 3.07(1H,d,J=9), 3.05(1H,d,J=15), 2.68–2.59(4H,m), 2.08–2.03(1H,m), 1.86–1.71(2H,m), 1.71(3H,s)
- Dithiane 5: 1H-NMR(300 MHz,CDCl3): δ 6.06(1H,s), 5.69–5.53(1H,m), 5.08–4.98(2H,m), 3.82(1H,s), 3.88–3.79(1H,m), 3.79(3H,s), 2.89(1H,t,J=12), 2.73–2.45(5H,m), 2.34–2.10(3H,m), 1.87(3H,s), 1.92–1.78(1H,m)
- Bicyclo[4.2.1]nonenedione 6: 1H-NMR(300 MHz, CDCl3): δ 5.97(1H,s), 5.67–5.51(1H,m), 5.03(1H,d,J=18), 5.02(1H,d,J=18), 3.76(3H,s), 3.20(1H,3), 3.03–2.94(1H,m), 2.71 (1H,dd,J=19,9), 2.50(1H,dd,J=8,14), 2.43(1H,d,J=17), 2.35(1H,d,J=19), 2.26(1H,dd,J=5,17), 2.19(1H,dd,J=7,14), 1.83(3H,s)
- X-ray diffraction study of 6: Crystalline 6 was obtained from ethanol solutions. The unit cell parameters were obtained through a least-squares analysis of the experimental diffractometer settings of 15 reflections with 2⊘ > 55°, using Cu Kα monocromatic radiation (λ=1.5418 A): a = 15.747(2), b = 7.807(1), c = 16.737(2)A, β = 116.34(1)°, V = 1844(1)A3. Space group P21/C was assigned on the basis of systematic absences OkO (k = 2n + 1). hO1 (1 = 2n + 1). The crystal density, D(obs) = 1.33 g cm-3, D(calc) = 1.32, for Z = 4, C18H22O4S2) was measured by flotation in hexane-carbon tetrachloride mixtures. A total of 3423 reflections were measured on a Syntex P21 diffractometer at 23°C using the ⊘-2⊘ variable scan technique and were corrected only for Lorentz-polarization factors. The structure was solved by direct methods and refined by full matrix least-squares analysis on the basis of 2502 “observed” reflections with I ε 30(I). The hydrogen positions were evident on difference maps. All hydrogens were introduced in idealized positions and assigned isotropic temperature factors; however, no hydrogen parameters were refined. The least-squares weights, w = ε-2(Fε) were calculated with the assumption that [sgrave]-2(I) = ε2 + (pI)2 where ε is a statistical counting error and p = 0.04. The refinements, assuming anisotropic motion for all C, O, S atoms, converged at R = 0.047, Rw = 0.061
- Turnbull , K. W. , Gould , S. J. and Arigoni , D. 1972 . J. Chem. Soc. Chem. Comm. , : 597 For a structurally related bridgehead enolate derived from the monoketone longicamphor, see